In normal dot matrix printers, the wires are activated to strike an inked ribbon which is impressed against the document being printed and with the latter being backed-up by suitable means, such as a platen or plate means. The problems with such printers are well known in that the wires get dirty, create smudgy copy, and the ribbons dry out, fray and generally have to be replaced quite frequently in the normal course of business.
Another technique involves the use of a smooth ink carrying transfer roller whereby the wires of the dot matrix print mechanism impinge on the backside of the workpiece and push the document in a negative impression manner against the transfer roller to pick up or absorb an array of ink producing the correct symbolism on the frontside of the workpiece. Devices, such as the latter ones, have distinct problems in that the ink, through gravity, tends to go to the edge of the roller and drip off making an undesirable mess. Additionally such devices tend to produce spots and bubbles of ink which cause smudging of the copy.
In offset and gravure printing of ink fountain applicator roll is generally used. This roll has a cellular type surface. The roll rotates in an ink fountain so the cells in the surface will pick up ink. The surface is doctored to remove excess ink and then depending upon the type of printing, the ink is transferred to a printing roll or blanket or the like. The cells in the surface of the applicator roll are provided to give an accurate and metered amount of ink or other material which is to be applied.
Transfer, applicator, and metering rollers of varying material compositions can be found in the art, i.e., the U.S. Pat. Nos. to Broderick--3,924,313; Fadner et al.--4,537,127; and Jenkins et al.--4,566,938. These are representative of disclosures of transfer rollers which utilize engraved, etched or other forms of produced indentations for moving quantities of ink or other materials from one location to another.